[Phytoecdysones and iridoids from Vitex megapotamica]

HPLC analysis of phenolics compounds and antioxidant capacity of leaves of Vitex megapotamica (Sprengel) Moldenke

Vitex megapotamica (Sprengel) Moldenke belongs to the Verbenaceae family and is popularly known as "tarumã". The antioxidant capacity of fractions and crude extract from the leaves of V. megapotamica were determined in this study through the capacity to remove reactive species and phenolic compounds were quantified in the various fractions. The IC50 (DPPH) ranged from 14.17 ± 0.76 to 37.63 ± 0.98 µg/mL. The ethyl acetate fraction might contain the strongest lipid peroxidation inhibitory compounds with an IC50 of 16.36 ± 5.09 µg/mL, being also the one with the highest content of polyphenols (522.4 ± 1.12 mg/g), flavonoids (220.48 ± 0.30 mg/g) and condensed tannins (3.86 ± 0.53 mg/g). Compounds quantified by HPLC/DAD in the crude extract and fractions were chlorogenic and rosmarinic acids. Higher dosages of the extracts were more effective in reducing levels of plasma protein carbonyls and were also shown to be able to remove reactive species by a 2',7'-dichlorofluorescein diacetate assay, reducing oxidative stress in all tested fractions. Results obtained indicated that V. megapotamica exhibits good potential to prevent diseases caused by the overproduction of free radicals and it might also be used as a potential source of natural antioxidant agents.

Effect of crude extract and fractions from Vitex megapotamica leaves on hyperglycemia in alloxan-diabetic rats

The effect of the crude extract, ethyl acetate and n-butanol fractions from Vitex megapotamica (Spreng) Moldenke on glycemia was investigated in diabetic rats. Oral administration of crude extract significantly reduced serum glucose levels in both normal and diabetic animals. In normal rats, serum glucose lowering was observed with 400 and 800 mg/kg at 2 and 2-3h, respectively after oral crude extract treatment. Nevertheless, the hypoglycemic effect of Vitex megapotamica in diabetic rats was evident at 1 and 2h and from 1 to 3h after treatment with 400 and 800 mg/kg, respectively. The ethyl acetate as well as n-butanol fractions were able to diminish glycemia in diabetic animals. The ethyl acetate fraction (400 and 800 mg/kg) produced the maximum hypoglycemic effect (28 and 20%, respectively) in diabetic rats and the same dose of the n-butanol fraction reduced the hyperglycemia only by 11% at 1h after treatment. Additionally, in hyperglycemic normal rats neither crude extract nor ethyl acetate fraction modified the glucose tolerance and the known tolbutamide effect on insulin release was clearly observed in this group. Thus, this study shows that Vitex megapotamica has an anti-hyperglycemic action, is able to ameliorate the diabetic state and, probably, is a source of hypoglycemic compounds.

Iridoid glycosides from Gmelina philippensis

Six new iridoids, 6-O-alpha-L-(2"-O-, 3"-O-, 4"-O-tribenzoyl)rhamnopyranosylcatalpol, 6-O-alpha-L-(2"-O-, 3"-O-dibenzoyl, 4"-O-cis-p-coumaroyl)rhamnopyranosylcatalpol, 6-O-alpha-L-(2"-O-, 3"-O-dibenzoyl, 4"-O-trans-p-coumaroyl)rhamnopyranosylcatalpol, 6-O-alpha-L-(2"-O-benzoyl, 3"-O-trans-p-coumaroyl)rhamnopyranosylcatalpol, 6-O-alpha-L-(2"-O-, 3"-O-dibenzoyl)rhamnopyranosylcatalpol, and gmephiloside as well as five known monoacyl and diacyl rhamnopyranosylcatalpol derivatives were isolated from the aerial parts of Gmelina philippensis. Their structures were established by spectroscopic means. Additionally, the known iridoids catalpol, geniposidic acid, gardoside, and 8-epi-loganic acid were identified and quantified by GC and GC-MS. The taxonomic significance of rhamnopyranosylcatalpol derivatives and iridoid acids as chemical characters is discussed.